Apparatus and method for laser machining

Abstract

A laser machining device includes a laser oscillator, a laser machining head, an optical fiber transmitting the laser beam oscillated by the laser oscillator to the laser machining head, and an assist gas supply supplying an assist gas of oxygen to the laser machining head. The optical fiber includes a remover removing a clad transmitting beam or reducer for reducing the beam. The laser beam leaked from the core of the optical fiber into the clad is absorbed by a beam absorber at the remover. The structure ensures a high quality surface with no irregularity on the metal surface cut by the laser beam projected from the machining head.

1 - 17 . (canceled) 
     
     
         18 . A laser machining method using a laser machining apparatus, said apparatus including a laser oscillating section for oscillating a laser beam; a laser machining head; an optical fiber, including a core and a clad disposed around said clad, for transmitting said laser beam oscillated by the laser oscillating section into the laser machining head, said optical fiber cooperating with the laser machining head to form a beam transmitting section; and an assist gas supply for supplying an assist gas of oxygen to the laser machining head; wherein said laser beam is transmitted through said optical fiber and projected against a work to cut the work while supplying said assist gas to a cutting point of said work,
 the method comprising:   removing or reducing said laser beam transmitting in said clad of said optical fiber or said laser beam projected from the clad so that an energy density of said laser beam transmitted from said clad and measured on said work is 15 kW/cm 2  or less.   
     
     
         19 . The method of  claim 18 , wherein said laser oscillating section includes a fiber laser oscillator. 
     
     
         20 . The method of  claim 18 ,
 wherein said laser oscillating section includes a plurality of laser oscillators;   wherein said beam transmitting section includes a plurality of first optical fibers having one ends each connected to said laser oscillators, and a second optical fiber having one end connected to said laser machining head and the other end connected to said one ends of the first optical fibers so that said laser beams oscillated by said laser oscillators are transmitted into the second optical fiber; and   wherein each of said first optical fibers and/or said second optical fiber includes said portion for removing or reducing said laser beam transmitting in said clad thereof.   
     
     
         21 . The method of  claim 20 , wherein each of said laser oscillators includes a fiber laser oscillator. 
     
     
         22 . The method of  claim 18 ,
 wherein said laser machining head includes an optical system for guiding said laser beam from said optical fiber toward a work to be machined, said optical system including an aperture plate for transmitting said laser beam projected from said core and cutting off said laser beam projected from said clad.   
     
     
         23 . The method of  claim 18 , wherein said optical fiber includes a portion in which said clad is exposed, said exposed portion having an outer diameter which is continuously reduced toward a beam output port of said core and including a smoothed outer peripheral surface. 
     
     
         24 . The method of  claim 18 , wherein said optical fiber includes a portion in which said clad is exposed, said exposed portion having an outer diameter which is reduced stepwise toward a beam output port of said core and including a smoothed outer peripheral surface. 
     
     
         25 . The method of  claim 18 , wherein said optical fiber includes a portion in which said clad is exposed, said exposed portion having enlarged diameter portions and reduced diameter portion provided alternately and including a smoothed outer peripheral surface. 
     
     
         26 . The method of  claim 18 , further comprising:
 a first retainer for retaining a portion of said optical fiber, adjacent said beam output port,   a second retainer for retaining a jacket of said optical fiber, and   a cylinder for enclosing said optical fiber and holding said optical fiber through said first and second retainers.   
     
     
         27 . The method of  claim 18 , wherein said work is made of material capable of being cut by heat provided from said laser beam. 
     
     
         28 . The method of  claim 26 , wherein said material of said work is iron. 
     
     
         29 . The method of  claim 26 , wherein said material of said work is mild steel.